High Flow Cat and Emissions (Utah)

[Scott Long]

My girlfriend just bought a 2011 A4 2.0T quattro 6-speed. The previous owner said he hollowed out the cat when they replaced the turbo. He didn't live in a county that does emissions. It keeps throwing the P0420 Catalyst Efficiency Below Threshold code. We have to get the car to pass the emissions test (OBD-2 scan and visual) so I was wondering if anyone has passed with a high flow cat and an O2 spacer, or if a high flow cat (USP 200 cell HFC) will cause the catalyst efficiency code still.

I have also seen some cheap cats on eBay for under $150 not sure how well they work. We are going to do an IE stage 1 tune on it and eventually will go stage 2 and that requires a high flow cat anyhow, so I'd rather not buy an expensive $400+ cat unless I need to swap it and flash the car back every damn year to pass emissions. The IE stage 2 tune I believe turns off the rear O2 but I'm not sure if they can tell in the emissions scan as long as the heated O2 and catalyst show "ready".

[JLAllroad]

My girlfriend just bought a 2011 A4 2.0T quattro 6-speed. The previous owner said he hollowed out the cat when they replaced the turbo. He didn't live in a county that does emissions. It keeps throwing the P0420 Catalyst Efficiency Below Threshold code. We have to get the car to pass the emissions test (OBD-2 scan and visual) so I was wondering if anyone has passed with a high flow cat and an O2 spacer, or if a high flow cat (USP 200 cell HFC) will cause the catalyst efficiency code still.

I have also seen some cheap cats on eBay for under $150 not sure how well they work. We are going to do an IE stage 1 tune on it and eventually will go stage 2 and that requires a high flow cat anyhow, so I'd rather not buy an expensive $400+ cat unless I need to swap it and flash the car back every damn year to pass emissions. The IE stage 2 tune I believe turns off the rear O2 but I'm not sure if they can tell in the emissions scan as long as the heated O2 and catalyst show "ready".

You will show catalyst inefficiency unless you meet the stock parameters of catalyst functionality, a high flow catalyst will not meet these parameters and tunes made to work with HFC generally do so by keeping the rear O2(catalyst monitor) from ever reaching readiness, said another way you need an OE catalyst.

That said, some state/county emissions allow a certain amount of monitors to pass without hitting readiness.


Sent from my iPhone using Audizine Forum

[Scott Long]

I figured the stage 2 tunes from APR, IE, etc probably end up turning off the rear O2 readiness since the high flow cat is going to increase flow so the rear O2 won't see enough difference from the front O2. On my B6 tune it's turned off but I don't have to do emissions since I have it registered out of state. I can do the spacer or the tune, but I don't want to spend the money if it's going to cause it to still not pass. I know some guys flash back to stock and put the stock cat pipe back on every year or every other year. It's a pain in the ass to do and I would rather do it once and be done.

[JLAllroad]

I figured the stage 2 tunes from APR, IE, etc probably end up turning off the rear O2 readiness since the high flow cat is going to increase flow so the rear O2 won't see enough difference from the front O2. On my B6 tune it's turned off but I don't have to do emissions since I have it registered out of state. I can do the spacer or the tune, but I don't want to spend the money if it's going to cause it to still not pass. I know some guys flash back to stock and put the stock cat pipe back on every year or every other year. It's a pain in the ass to do and I would rather do it once and be done.

APR stg1 is now emissions compliant, with the stock catalyst.

I have not seen anyone have a sure fire combination of spacers/elbows/or mini catalysts that work to fool the second O2.


Sent from my iPhone using Audizine Forum

[bb-tt]

I figured the stage 2 tunes from APR, IE, etc probably end up turning off the rear O2 readiness since the high flow cat is going to increase flow so the rear O2 won't see enough difference from the front O2. On my B6 tune it's turned off but I don't have to do emissions since I have it registered out of state. I can do the spacer or the tune, but I don't want to spend the money if it's going to cause it to still not pass. I know some guys flash back to stock and put the stock cat pipe back on every year or every other year. It's a pain in the ass to do and I would rather do it once and be done.

Ie stg 2 did not code out o2 sensor and and worked with hfc

[K_Estes]

Ie stg 2 did not code out o2 sensor and and worked with hfc

same - no CEL once I flashed it after adding HFC.

[Scott Long]

Ok good to know. Guess when the time comes for stage 2 I'll consider IE HFC and tune. I am probably going to go with Ward Performance Tuning stage 1 since I already have HP Tuners for my truck and am familiar with it.